Building Green: An Update on Atlanta's Green Infrastructure Approach

Transcription

1 City of Atlanta Mayor Kasim Reed Department of Watershed Management Building Green: An Update on Atlanta's Green Infrastructure Approach Cory Rayburn, CPESC, CFM Environmental Program Manager SESWA Spring Seminar April 17,

2 Presentation Outline Overview of Atlanta s program and how it s unique First two years of Implementation Single Family and Small Commercial design manuals Challenges and Solutions Common green infrastructure practices used Recent public green infrastructure projects Southeast Atlanta Green Infrastructure Initiative combined sewer capacity relief Historic 4 th Ward economic development 2

3 Why use green infrastructure in Atlanta? Environmental Protection Improves water quality Supports Mayor Reed s sustainability initiatives Compliance Complies with NPDES permit Removing Barriers Prepares the City for potential changes in federal stormwater rules Community Addresses drainage issues in redeveloping historic neighborhoods Maximizes infrastructure investments by further reducing combined sewer overflows and flooding 3

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5 Amended Stormwater Ordinance Added Green Infrastructure requirement for new and redevelopment projects Process for success Technical Advisory Committee Robust stakeholder involvement Give and take approach Outreach, education, and technical guidance documents Unanimous Council approval in Feb

6 What s makes Atlanta unique? Requires green infrastructure on single family infill and commercial development/redevelopment 1.0 Runoff Reduction Volume (RR v ) Mandatory versus voluntary* No direct financial incentive Low threshold for compliance * Allows for fallback to 1.2 Water Quality (80% TSS reduction) upon showing 1.0 RR v is not possible on the given site written rationale and separate approval required 6

7 Who has to do what? Single family development (RR v only) New or infill home construction Large additions (> 1,000 ft 2 ) Small commercial category (RR v only) 500-5,000 ft 2 added or replaced impervious surface Commercial adding > 5,000 ft 2 Full blown stormwater management plan and hydro study Rate Reduction up to 25-year storm 100-yr no increase in peak discharge rate All Commercial projects Infiltration testing Pre-submittal consultation Site-specific Operation and Maintenance Plan 7

8 The Pioneer Projects Green Roof - Atlanta City Hall Cistern & Green Roof - Southface Bioretention - Adair Park Bioretention - 14 th St DWM office Bioswale - Fernbank Museum Porous Concrete - Felder St Pervious Pavers - English Park Wet pond, wetlands bench, sewer capacity relief, urban reforestation - Historic Fourth Ward Bioswale - Klaus Building - GT campus 8

9 Recent Installs Bioretention - Kelly St Porous Concrete - Delia s Chicken Sausage Stand Bioswale - Edgewood Townhomes Bioretention - Whitehall Terrace ROW Cistern SFR - Leslie St Permeable Pavers - Urban Market on Howell Mill Permeable Pavers - 6 th and Juniper Bioretention - Regions Bank Permeable Pavers - Lakemoore Townhomes 9

10 Adopted the Coastal Stormwater Supplement PROS Provides design criteria and credit system for green infrastructure Dependant on soil type CONS Does not address SFR or Small Commercial Created SFR and Small Commercial design manuals Atlanta Regional Commission (ARC) in process of updating Blue Book 10

11 Simplified Design Approach 11

12 SFR Manual Provides a list of acceptable practices Reduces the need for complicated calculations Provides tear-off details and construction specification for each practice Simplifies the review and approval process 12

13 General Info & Tear-off Details 13

14 Easy-to-Use Sizing Tables Impervious Area Treated Design Options Practice Size Modified French Drain Example Options within practical range Accommodate actual rainfall and runoff data Allows for median infiltration duration Assumes in/hr infiltration rate 14

15 Small Commercial Manual For projects that add/replace between 500 and 5,000 ft 2 of impervious surface Catered to small urban redevelopment and addition projects Supplement to CSS and Blue Book Provides clarification to specific issues 15

16 Step-by-step Processes 16

17 Simplified RRv Calculation 17 Example: 3,800 ft 2 addition

18 Sizing Charts for each Practice 18

19 Example Design 19

20 Construction Sequence Extensive green roof installation 20

21 Retrofit examples - Landscape Islands 21

22 Typical Details 22

23 Innovative designs included Upturned S Underdrain Creates saturated zone Aids in denitrification Additional infiltration in poor draining soils 23

24 Example Landscape Plans 24

25 Maintenance Checklists 25

26 Tracking green infrastructure with GIS 270+ Commercial 1,100+ Single Family Residential GIS attributes contain: Owner Date of completion Copy of I&M agreement Inspections information Green infrastructure BMPs Detention BMPs Runoff Reduction Volumes 26

27 Challenges & Solutions 27

28 Green infrastructure can compete for space Creativity with site layout Upfront coordination between Civil, LA, and Architect Dual purpose practices: permeable pavement landscape islands bioretention green roof underground detention/infiltration systems Able to meet tree planting and runoff reduction requirements with one practice 28

29 Appropriate site layout? 29

30 Infiltration Practices in Atlanta Soils analysis required for all commercial sites Infiltration rates, high water table, bedrock, contaminated soils Clay soils and compaction Loosening compacted soils on redevelopment sites Prevent compaction during construction Innovative designs (upturned underdrain) to encourage surface drainage and promote infiltration in clay soils Erosion control Phasing installation to prevent sedimentation issues Installation of appropriate BMPs 30

31 Erosion control and phasing 31

32 Erosion control and phasing 32

33 Common Practices on Commercial Sites Bioretention/Bioswales/Stormwater Planters Infiltration below an underground detention system Permeable Pavement Infiltration Trenches/Dry Wells Rainwater Harvesting/Cisterns Green Roof (only 2) < 20% of sites fell back on old Water Quality standards for part or all of the volume requirement 33

34 WQ Fallback Requires written rationale and separate approval Extreme economic hardship or physical impossibility Must consider infiltration-alternative BMPs (lined stormwater planters, rainwater harvesting & green roofs) Rainwater harvesting reuse potential depends on type of project Irrigation, evaporative cooling, toilet flushing 34

35 Return on Investment Grand Hyatt in Buckhead retrofit Rainwater Harvesting: 50,000 ft 2 rooftop Evaporative cooling towers and toilet flushing Cost of project: $100, Annual savings: $42, ROI = 2.4 years 35

36 Green Roof Costs and Benefits $10-$24/ft 2 Extends life of roof Cooler air intake and insulation benefits = energy savings Amenity potential 36

37 Underground Infiltration Systems Saves space compared to traditional dry/wet ponds Appropriate pretreatment required Surface drainage area to infiltration area ratio May require additional aggregate under system for structural support (without compacting subsoils) Geotextile underliner vs. choker stone Erosion control during installation! 37

38 Common Practices on SFR 55% Dry Wells 21% Rain Gardens 10% Modified French Drains 6% Permeable Pavement 5% Cisterns (not rain barrels) 3% Vegetated Filter Strips 38

39 Southeast Atlanta Green Infrastructure Initiatives Combined Sewer Capacity Relief 39

40 Custer CSO Basin Location Heart of Atlanta Highly impervious Piped Streams Repeated Flooding 40

41 Contributing Conditions Point of Surface Flooding July 2012 (Peoplestown) 41

42 Short-term Projects First 6 months 42

43 Curb Extension Whitehall Terrace - converted parking spaces into bioretention area 43

44 Bioretention and Cistern Rosa Burney Park - converted area with poor soil conditions into bioretention 44

45 Bioretention Windsor Street - redirected runoff from street into new bioretention area 45

46 Bioretention Kelly Street - converted paved street into bioretention area 46

47 Intermediate Projects Media lot vault Completed Feb 28, 2014 Permeable Pavers Design-build contractor selected Construction began 3/31/2015 Estimated completion date Spring of 2016 Media Lot Vault 47

48 Permeable Pavers ~6 miles of permeable pavers: Mechanicsville Peoplestown Summerhill 48

49 Historic Fourth Ward Park Opened Combined Sewer Capacity relief 49

50 Historic Fourth Ward Park Opened Combined Sewer Capacity relief 50

51 Public-Private Partnership 51

52 Which would you prefer? 52

53 Spurring Redevelopment Plans for pond 2010 finalized, adjacent Construction on pond condobegins construction pond continues begins 2011 Pond complete Adjacent park and Beltline underway ~$500 Million in redevelopment Apartments, condos, & Ponce City Market underway Beltline complete 2014 Apartments, condos, Ponce City Market nearing completion Masquerade redevelopment underway 53

54 Mayor s Commitment It is my goal for Atlanta to become one of the top tier sustainable cities in the nation -Mayor Kasim Reed 54

55 Questions? Cory Rayburn, CPESC, CFM City of Atlanta Department of Watershed Management David Mason, PE, D. WRE CDM Smith (615)